Recently we at Program4 Engineering, Inc. met the challenge of developing a flexible batching system for a contract food manufacturer who needed the ability to define several batching processes using the same pieces of equipment combined in different ways. In some cases a batch vessel would become, once its own batch was complete, a pre-mixed ingredient to another batch vessel. To raise the bar another notch, the facility did not possess any similarly sophisticated control systems, or operating personnel who might be familiar with such systems, so the control system had to be very operator-friendly and easy to use.

Using GE Fanuc Automation’s iFix™ and a Rockwell PLC, Program4 developed a Flexible Batching System. The software engineered by Program4 not only enables the Process Engineer or Operator to set up and run any INGREDIENT in any orderbut also enables the operator to set up and run any OPERATION in any order.

This is set up with the iFix Recipe Handler where the Recipe consists of a set of Phases for each Unit. With this Solution, which we are calling Program4 Flexible BatchingSM , the sequencing in done in the PLC, not in the SCADA PC or Batching Software.

Program4’s Flexible Batching Solution has many of the advantages of the ISA S88 Standard at a moderate cost.

Read on for a full description, but if you would like a demonstration call Program4 Engineering at 610 380-9990 Ext. 306.

In most batching applications, dedicated production lines lend themselves to very user-friendly batching systems and interfaces. With a set sequence of ingredient additions, ingredient sources, cooking cycles, and transfer to dedicated use or storage tanks, the batching sequence is predicable and can be highly automated. Minor ingredient hand-adds can be made in a structured manner through operator prompts or confirmations, and the recipe consists of quantitative data such as ingredient and temperature setpoints. Similarly, a standard Batch Record or report can easily be generated, because the ingredients, sequences, and operations are predictable. The only deviation from the set batching sequence might be a Semi-Auto mode that would allow adjustment of setpoints or execution order. Program4 has provided many such batching systems over the years.

Today’s fast-paced manufacturing environments, however, can demand flexible production lines capable of making a variety of products with a minimum of equipment or software adjustment. This presents problems to the process control programmer, as all possible combinations of equipment and ingredients must be possible, and the recipe becomes less predictable in size and structure.

The ISA S88 batching standards provide a vision and framework for flexible batching in which processes and recipes are defined at a higher level, divorced from the actual equipment and operating software. A Unit-based approach (where a Unit is a vessel or piece of process equipment and its associated devices) allows the recipe to define a set of operations or Phases that take place using whatever Units are required. Ingredient sources and product destinations are flexible, as ingredient additions and product transfers are phases within the recipe and may be specified in any combination or order.

While in a perfect world the S88 offers an elegant solution to batch processing, a drawback is the complexity and sophistication of the high-level control system, and thus the cost of implementation. Many of the premier process and HMI software providers have come forth with their S88 solutions such as Wonderware®’s InBatch™, GE Fanuc’s iBatch®, Rockwell’s RSBizWare™ Batch etc. All of these products involve licensing costs and a steep learning curve, and are aimed at a high-level operational staff. While these products may be suitable for a large scale production facility in the Pharmaceutical or Chemical manufacturing environment, they can be overkill in a food and beverage plant.

The approach Program4 Engineering took was to define a set of operations or phases for each unit. The process units consisted of:

• Pre-Mix Tank
• Mix Tank
• Liquid Blend Tank
• Two Dough Mixers.

In addition, two Ingredient Silos can feed either the Mix or Pre-Mix Tank. The Liquid Blend Tank acts as an ingredient source for the Dough Mixers. The Pre-Mix tank is an ingredient source for the Mix Tank, which supplies a Syrup Use Tank, which in turn is an ingredient source for the Dough Mixers. In some recipes, the Mix Tank is not used, but acts as a pass-through vessel between the Pre-Mix Tank and Syrup Use Tank.

Phases are defined as:

• Silo 1 Addition
• Silo 2 Addition
• Hand Addition
• Water Addition (to Pre-Mix and Mix Tanks)
• Pre-Mix Addition (To Mix Tank)
• Liquid Blend Addition (to Mixers)
• Syrup Addition (to Mixers)
• Heating
• Mixing
• Operator Prompt and Acknowledge
• Hold
• Transfer

The Recipe then consists of a set of Phases for each Unit. If a Unit was not needed for a particular product, it’s recipe would remain blank. For each required unit, the Phases could be selected in any order. Each Phase contains up to three variables that pertain to that phase. Ingredient addition phases, for instance, have variables for Setpoint and Percent Tolerance. Hand Add Phase has a variable that points to the ingredient SKU. The Mixing Phase has a time preset, while the Heating Phase has a temperature setpoint. Operator Prompt Phase has a script number that selects the required message to be displayed. Each Phase also includes an Agitator Run flag (on/off) that determines whether the agitator runs during the Phase, and a Watchdog Time that will trigger an alarm if the Phase takes too long to execute.

The Recipe Management pages are fully interactive. There is a page for each Unit except the Syrup Use Tank, which has no batching sequences, and the Dough Mixers, which share a single recipe page. As each Phase is selected, the appropriate variable fields are displayed and identified. Pull-down lists for such variables as Operator Prompt and Minor Ingredient are available. Recipes can be saved and loaded, or saved under a new name.

During batching operations, the Batch Monitor page provides the Operator with a display of the batching sequence. The Phases are displayed in the order specified by the recipe. Each batch is initiated by the Operator through a Batch Start button. Each Phase is highlighted as it executes, and actual values and deviations (in e.u. and percent) are displayed for each Phase. These setpoints, actual values, and deviation percentages are saved as an electronic batch report at the end of each batch. At each Hand Addition Phase, the Operator is prompted to add the specified ingredient and confirm its addition. Similarly, at the specified Prompt and Acknowledge Phases, the Operator may be prompted or asked questions such as, “Are all materials dissolved?” or “Is Mixer empty?” At the end of each Phase, the system moves on to the next Phase in the sequence, until an empty Phase is reached, at which point the Unit returns to an Idle state to await the next batch.

In cases where one Unit is an ingredient source to another, the source Unit stops at a Hold Phase and waits for the destination Unit to request product. If the source Unit is below a set level when the Addition Phase is complete, it returns to an Idle state so as to be available for a new batch. If it is not empty, it returns to the Hold Phase to wait again. (The Operator can also initiate a batch from the Hold Phase.)

Despite their lack of experience with sophisticated control panels, the Operators took to the system very rapidly. They liked the checklist aspect of having the Hand Additions part of the sequence, as it helped keep them from skipping ingredients.